Etaler backend re-architecture about etaler HOT 1 OPEN

Quick update, this modified code is slightly faster than the above code. 1. Returns a reference to std::function and reads a reference of std::function from std::any. 2. Use a std::string_view as key instead of std::string. But this feature requires C++20

 struct BackendBase
 {
         std::map<std::string, std::any> funcs_;
 
         template<typename Class, typename Return, typename ...Args>
         void expose_method(const std::string& name, Return(Class::*func)(Args...))
         {   
                 funcs_[name] = std::function<Return(Args...)>([this, func](Args ... args) { 
                         (static_cast<Class*>(this)->*func)(args...);
                 }); 
         }   
 
         template <typename Func>
         const std::function<Func>& get_method(const std::string_view name)
         {   
                 return std::any_cast<const std::function<Func>&>(funcs_.at(name));
         }   
 };

This is not the final design tho. I still want to remove the use of std::function and use a custom, more specific class. Hopefully the method wrapper can ensure no allocation what so ever.

Update: The current lambda needs exactly 24 bytes of storage space on 64bit systems. Which is exactly how much space libc++'s std::function have for small functions. No heap allocations. We are good in that regards :)

from etaler.